Some prostaglandin derivatives are known to have anti-pruritic effects, and there is disclosed the use of such prostaglandin derivatives as prophylactic or therapeutic external preparations for diseases such as atopic dermatitis and scabies (refer to Patent Document 1). For example, disclosed is a prophylactic or therapeutic agent, for pruritic symptoms, containing a prostaglandin derivative represented by the following formula (I):
a pharmaceutically acceptable salt thereof, or a hydrate thereof (hereinafter, referred to as a “compound of formula I”) as an active ingredient.
Such a prophylactic or therapeutic agent, for atopic dermatitis or the like, containing the compound of formula I as an active ingredient is provided as an external preparation such as an ointment preparation or a lotion preparation (refer to Patent Document 1).
However, it is known that the compound of formula I is scarcely soluble in water and that the storage stability of the compound of formula I is significantly deteriorated when the compound of formula I is in a water-dispersed state or the like (refer to Patent Document 2).
Accordingly, in order to provide an aqueous external preparation, such as a lotion preparation, containing the compound of formula I, a technique has been demanded which allows the compound of formula I to uniformly dissolve in an aqueous external preparation and thereby ensures the storage stability of the compound of formula I.
Patent Document 1: International Publication No. WO2004/014394
Patent Document 2: International Publication No. WO2006/085655